function isEmpty(obj) {
    if (obj == undefined) { // 包含 null 和 undefined
        return true;
    } else if (typeof obj === "string" || Array.isArray(obj)) {
        return obj.length == 0;
    } else {
        return false;
    }
}

function guid() {
    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function (c) {
        let r = Math.random() * 16 | 0,
            v = c == 'x' ? r : (r & 0x3 | 0x8);
        return v.toString(16);
    });
}

function uuid() {
    let s = [];
    let hexDigits = "0123456789abcdef";
    for (var i = 0; i < 36; i++) {
        s[i] = hexDigits.substr(Math.floor(Math.random() * 0x10), 1);
    }
    s[14] = "4"; // bits 12-15 of the time_hi_and_version field to 0010
    s[19] = hexDigits.substr((s[19] & 0x3) | 0x8, 1); // bits 6-7 of the clock_seq_hi_and_reserved to 01
    s[8] = s[13] = s[18] = s[23] = "-";
    return s.join("");
}

function removeDuplicates(arr) {
    return [...new Set(arr)];
}

function removeEmpty(arr) {
    return arr.filter(item => item != undefined && item.trim() != "");
}

function removeDuplicatesAndEmpty(arr) {
    return removeDuplicates(removeEmpty(arr));
}

module.exports = { isEmpty, guid, uuid, removeDuplicates, removeEmpty, removeDuplicatesAndEmpty }